DYNAMIC MICROORGANISM GROWTH MODELING FOR SHELF LIFE PREDICTION: APPLICATION TO COOKED AND BRINED SHRIMPS

Listeria monocytogenes growth data in cooked and brined shrimps under different storage temperatures (0°C, 5°C, 8°C, 15°C and 25°C) were selected from Combase (Dalgaard and Jørgensen, 2000) to develop a dynamic model for shelf life prediction. Based on a multi-step parameter identification procedure, the Baranyi model was fitted for the growth curves of L. monocytogenes, coupled with the Ratkowsky square root model and a sigmoidal function as secondary models for the temperature dependency of the maximum specific growth rate and the maximum cell density respectively. Uncertainty on the prediction of the global growth model was analyzed and the 95% confidence intervals of the predicted microorganism concentration time profiles were determined. Based on these latter, shelf life estimation was 42-53 days, 9-11 days, 3-4 days at 8°C, 15°C and 25°C respectively according to the upper limit of L. monocytogenes in ready-to-eat products, 100 cfu/g. These results are in agreement with those presented in (Dalgaard and Jørgensen, 2000), which illustrates the shelf life prediction abilities of the proposed dynamic growth model.